Oil well casing perforator



2 Sheets-Sheet 2 J. B. M ELHENY INVENTOR. rb/m/ 15. Ml x/zm I' Arralen/z/s.

OIL WELL CASING PERFORATOR Oct. 16, 1962 Filed April '7, 1958 Uited States Patent I 3,58,522 Patented Oct. 16, 1962 3,058,522 OIL WELL CASING PERFORATGR John B. McElheny, Fullerton, Calii, assignor to The Hydro-Peri Company, Downey, Califi, a partnership Filed Apr. 7, 1958, Ser. No. 726,709 4 Claims. (Cl. 156-554) This invention relates to oil well casing perforators.

Upon completion of an oil well drilling operation, tubular casing is used to line the well. This casing extends usually to the bottom of the well, although there may be several oil-bearing strata through which the well extends. It is customary to perforate the casing at one or more of the logged levels where such productive strata were found, so as to make it possible to remove the oil from such levels.

It is customary to provide explosive-propelled projectiles to effect perforation. Thus to fire such perforator devices, it is common to use a perforator gun, operated by a trigger mechanism to fire a cartridge, or to send an electrical impulse to a fuse or booster, the gun being lowered to the desired depth in the casing. In any case, the firing of the gun or its equivalent required the utilization of equipment at the top of the well, such as circuit controllers, or the like, for firing the cartridge or its equivalent.

It is one of the objects of this invention to provide an improved perforator, and that operates without the necessity of leading a current to a gun or its equivalent.

It is another object of this invention to make it possible to move the perforator mechanism downwardly of the well, and accurately to preset the level at which it will fire. The mechanism is preset, and automatically fires when it reaches the desired level.

The invention, in its broadest aspect, is not limited to any particular means for lowering the perforating mechanism into the well. Nevertheless, utilization of hydrostatic pressure for this purpose leads to advantageous results. -For example, it is unnecessary to use a lowering line.

It is accordingly still another object of this invent-ion to utilize a hydraulic force for lowering the perforating mechanism.

It is still another object of this invention to make it possible to fire an explosive charge in a simple manner at a specific level in a well.

It is still another object of this invention to provide a guide means for the descent of the perforating mechanism to the required depth, and to ensure automatic firing occurs just as soon as the mechanism leaves the .guide means. For example, the guide means may be a tube, cooperating with the mechanism during its descent, to prevent it from firing. The tube is arranged to end just above the level where the perforating is to occur. Just as soon as the restraint provided by the tube is no longer effective by the descent of the mechanism out of the tube, firing occurs.

It is another object of this invention to provide for firing of the mechanism by an appropriate means as soon as the mechanism leaves its guide. In one form, the firing is accomplished by fluid pressure available at the depth of firing. Other forms, utilizing a triggered spring, or an electric circuit including a flashlight cell, may as well be utilized.

It is another object of this invention to safeguard against inadvertent firing of the mechanism while it is out of the well. For this purpose a safety lock is provided, preventing operative movement of the firing mechanism until a sufficient depth is reached to release the lock by hydraulic pressure.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of several embodiments of the invention. For this purpose, there are shown a few forms in the drawings accompanying and forming part of the present specification. These forms will now be described in detail, illustrating the general principles of the inven tion; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

FIGURE 1 is a vertical sectional view, partly broken away of a well and a perforator mechanism therein, the mechanism being above the level at which the perforations are to be made;

FIG. 2 is an enlarged sectional view of the operating parts of the firing mechanism in its tubular guide;

FIG. 3 is a view similar to FIG. 2, but illustrating the firing position of the mechanism;

FIG. 4 is an enlarged sectional view taken along a plane corresponding to line 4-4 of FIG. 2', and

FIGS. 5, 6 and 7 are views similar to FIG. 2 of modified forms of the invention.

In the form illustrated in FIGS. 1 to 4, a well 1 is shown having well casing 2. Mechanism 3, illustrated in more detail in FIGS. 2, 3, and 4, is intended to descend into the well casing 2 and to provide the firing of an explosive charge or charges at a definite level. The explosive charges in this instance are shown in FIG. 1 enclosed in a thin tube 4 in which are located conical containers 5 strung lengthwise by linkages 6 and connected serially together by a fuse 7. The tube =4 may, of course, be omitted. Projectiles with spherical ends are enclosed with an explosive charge in the containers 5 and when the fuse or cord 7 is ignited, these charges explode, and send the projectile not only through the thin tube 4, but also through the well casing 2.

Since this type of explosive-propelled perforator bullet or projectile devices are now well-known, further description thereof is unnecessary. Especially is this the case, since the present invention relates more particularly to the manner in which the explosive charges are detonated.

In order to cause the mechanism 3 to descend, use is made of a guide 8 shown in the present instance as a tube, extending downwardly from the top of the well to a definite level.

This tubular guide 8 may be so arranged that the device 3 descends to the desired place where it is to operate the detonating or firing mechanism. The weight of the mechanism 3 may be sufiicient in some instances to move the mechanism 3 expeditiously through the guide 8, by gravity.

In order to assist the descent and to make the descent positive, hydrostatic pressure may be used. For this purpose, the mechanism 3 carries at its upper end a piston structure cooperating with the interior surface of tube 8. This structure sealingly contacts the inner wall of the tube 8. Thus, for example, a piston cup 9' of yielding material, such as rubber or leather, is joined to the supporting member 1-0 of device 3. This supporting member carries all of the important parts of the firing mech anism. This supporting member 10 has a generally cyindrical exterior surface having an upper projection 11 of reduced diameter. Attached to this projection 11 is a retainer disk 13. This disk is held in place by the aid of a screw 14 threaded into the top of the supporting member 10. The retainer disk 13 in cooperation with a collar 15 serves to clamp the cup to the member 10.

A vent hole 131: is provided in disk 13. Furthermore, the disk 13 has a depending flange 13b engaging a corresponding annular groove in the upper surface of cup 9.

The cup also has an upwardly projecting hollow portion 16 which is expanded by the hydrostatic pressure within it to urge the wall 16 forming the hollow portion outwardly against the interior surface of the tube 8. Thus, a piston structure is provided.

Liquid such as mud, water or the like, available at the top of the well, is intended to be pumped into the top of the tube 8 as by the aid of a pump 17. Accordingly, the weight of the liquid or fluid on top of the supporting member 10 creates a hydrostatic force, serving to urge it downwardly and outwardly of the bottom edge of the tube 8. When this occurs, the firing mechanism 3 is rendered active.

The supporting member 10 has a lower end 18 which is internally threaded for the reception of the threaded upper end =19 of a cylindrical body 20. A collar 21 is interposed between the top of the threaded portion 19 and the shoulder 22 formed on the supporting member 10. A pin 23 for performing the firing operation is guided in the projection 19 as by the aid of a bore 24-.

The firing pin 23 has an enlarged lower cylindrical portion 25 carrying the pin proper 26 at its lower end. The enlarged portion is sealingly accommodated within the bore 24 by the aid of one or more O-rings 27, located in annular grooves in the bore 24. In this way, well liquid is prevented from entering the body 20, and the detonating elements are kept dry.

The firing pin 23 is shown as provided with a head 28 (see also FIG. 4) having a lower tapered surface 28a. The taper forms an external conical surface, enlarging upwardly. Fluid pressure acting on the head 28 is intended to urge the firing pin 23 downwardly to the position indicated in FIG. 3, where it performs a firing operation as hereinafter explained.

The firing pin 23 is restrained while the mechanism 3 is within the tube '8, by the aid of a pair of pivoted arms 29 and 30. These pivoted arms have external surfaces contacting the inner surface of the tube 8 and are held by the tube in the restraining position of FIG. 2. These arms are located in slots 29a and 30a (see also FIG. 4) of the supporting member 10. For providing the restraint, each arm carries a latch 31 cooperating with the lower tapered surface 28a, and preventing downward movement of the pin 23. The pivots for the arms are formed by the aid of pins 32 at the lower ends of the arms.

As soon as the device 3 reaches the position below the tube 8 so as to free the arms 29 and 30, fluid pressure is effective to operate upon the head 28 for driving the pin 23 downwardly, and for performing the firing operation.

The level to which the lower end of the tube guide 8 extends thus determines the level at which the firing occurs. The level of firing is determined at the time the tube 8 is installed within the well casing 2.

The detonation of the devices destroys the mechanism 3 with all its associated parts, so that a new perforator can, if desired, be utilized in the same tube 8 which may be either raised or lowered as desired.

The body 20 i rendered fluid-tight against the entry of liquid to the firing mechanism as by the aid of another body section member 33. Thus, a fluid-tight enclosure is formed by the members 20 and 33. The projection 19 of member 33 forms the upper wall of the enclosure. This body member carries the tubular element 4 which .extends downwardly from the mechanism 3. It is also threadedly received in the internally threaded lower end 34 of body member 20. A cylindrical flange 35 is carried by the body member 20 and cooperates with an O-ring 36 to maintain the interior of the body member 20 in sealed relation.

The firing pin 26 is guided by the collar 37 disposed in a bore 38 at the upper end of the body 33. A firing cartridge 39 is aligned with the guiding bore 40 of the collar 37. This firing cartridge serves to detonate a booster charge 41. This booster charge 41 in turn is in firing relationship with the cord 42 leading to the fuse 7.

In order to maintain the sealed relationship where the cord 42 enters the lower end of the body 33, use is made of a. gland structure. Thus, there is a threaded gland member 43 engaging the lower end of the body 33. This member cooperates with packing 44 maintained in sealing relationship by the aid of a gland nut 45. The seal is effected around a thin copper tube 46 crimped around the cord 42.

in order to ensure that the mechanism may be safely withdrawn from the well in the event of failure of firing, provisions are made to permit liquid to enter within the interior of the body 20 and thus wet the cartridge 39. For this purpose, there is an enlarged bore 47 surrounding the lower end 25 of the firing pin 23. When the firing pin 23 reaches the end of its stroke, as shown in FIG. 3, water may enter through the bore 24 around the pin 23 and through the enlarged bore 47 to the cartridge 39.

When the mechanism 3 is placed into the tube 8, provisions are made for locking the pin 23 against firing until there is a suflicient fluid pressure within the tube 8 to release it.

For this purpose, as shown most clearly in FIG. 4, there is a locking pin 48 arranged radially of the head 28. This locking pin is provided with an annular groove accommodating a sealing O-ring 49. The head 28 has a transverse aperture 50 which is closed at one end. Accordingly, the pin 48 serves as a piston. When urged in wardly, it compresses the air in the bore 50, which creates a resilient force tending to move the locking pin 48 outwardly. The outer end of the pin 48 is located within a bore 51 which is somewhat larger in diameter than the pin 48.

To assemble the device, the pin 48 is manually urged inwardly when the device 3 is turned with respect to body 10, so as to align the pin 48 with one of the slots 29a or 30a. Then while it is held, the body 10 is turned so as to move the pin 48 out of alignment with the open slot, and the turning is continued until the pin 48 reaches the position of FIG. 4. The air pressure in bore 50 urges the pin outwardly to this locking position.

When thus first assembled with the tube 8, the outer end of the pin 48 contacts the bottom of the bore 51. However, as the mechanism 3 is lowered, sufficient fluid pressure is exerted on the outer end of the pin 48 to move it inwardly of the bore 50 against the air pressure and to unlock it. Accordingly, there is no danger when the mechanism 3 is handled that there be any inadvertent or accidental firing of the explosive, before it is moved into the well.

In the form just described, liquid pressure applied to the head 28 serves to move the firing pin 23 to the firing position. In the form shown in FIG. 5, the movement of the pin 52 is eifected by stored energy. Thus, the pin 52 has a lower head 53 forming a shoulder for a compression spring 54. The upper end of the spring 54 is confined by the flange 55 of a slidable spring cage 56. This cage 56 is slidingly received in the upper end 57 of the member 58 which carries the body 33a corresponding to body 33 of the form previously described.

The guide for the cage 56 is effected by the inwardly directed flange 60 of body 58, and an outwardly directed flange 61 on the cage 56. Appropriate O-rings 62 and 63 ensure against flow of fluid or liquid past the sliding cage 56.

As the fluid pressure increases on the top of flange 55 by descent of the mechanism in tube 8, the spring 54 is compressed against the upper surface of head 53. When the mechanism descends sufficiently to leave the tube 8, the arms 29 and 30 release the energy of the compressed spring; and the pin 59 is struck by the head 53. This pin 59 is sealingly guided by a collar 59a mounted in sealed position on top of the body member 33a.

In the form shown in FIG. 5, fluid pressure is utilized to store energy by compressing spring 54 and this energy is utilized for driving the firing pin 52 downwardly.

In the form shown in FIG. 6, the slidable cage member 56 is held in spring-compressing position at the time the firing mechanism is assembled in the tube 8. For this purpose, an inwardly projecting pin or screw 63a cooperates with the upper edge of flange 61 to hold the spring 54 in compressed position. As soon as the arms 29 and 30 release the head 28 of the pin 52, the spring pressure serves to urge the pin 52 downwardly.

In the form shown in FIG. 7, a firing pin 64 serves to operate a circuit controller for firing the booster explosive 65. This booster explosive is located above the fuse cord 42.

The body 66 supporting the cord 42 is supported in the intermediate body 67. This intermediate body provides a shoulder for an insulation member or collar 68 through which there is an aperture for the reception of the lower end of the pin 64. The insulation member 68 and an insulation collar 70 mounted in the upper end of the body 66 assist in defining a space for a dry cell 71. This dry cell 71 is surrounded by a cylindrical insulation member 72. Two opposite terminals of the cell are connected respectively to a wire 73 leading to the booster 65, and a wire 74 leading to a depressible contact arm 75. This arm 75 is in the path of movement of the pin 69 and is maintained in position by a hollow insulation member 76 located between the collar 68 and the body 72. A metal base 77 is disposed below cell 71 and also provides an anchor for wire 73.

When the pin 69 depresses the contact arm 75, the circuit is completed through the dry cell 71 and the booster explosive 65.

The inventor claims:

1. In a firing device adapted to be placed in a well and utilizing an explosive charge: a support adapted to be moved into the well; a fluid-tight enclosure carried by the support and having a wall; an explosive charge in the enclosure; said charge being incapable of firing when wet; a firing pin guided in the wall; and means whereby the pin is moved inwardly of the enclosure for firing the (23! explosive; said firing pin having such configuration as to maintain sealing relationship with the wall 'for only a part of its inward movement, so that fluid may enter the enclosure upon completion of the pin movement, for wetting the charge.

2. The combination as set forth in claim 1, in which the configuration of the pin is such that it has a portion of reduced diameter that defines a passage through the wall for the fluid when the pin moves inwardly.

3. In combination: a firing mechanism adapted to be placed in well casing: said mechanism including a longitudinally movable firing pin having a head; a guide for the descent of the mechanism; a restraint engaging the head of the pin and held in restraining position by the guide, said guide ending adjacent the level where the firing is intended to occur; a support for the restraint; the fluid pressure in the Well serving to urge the pin to firing position when the restraint is removed; and locking means operable to hold the pin against firing movement, except when the pin reaches a definite depth in the well, including a movable member engaging the pin, said member also engaging a recess in the support, and urged by fluid pressure to release the pin from the recess.

4. The combination as set forth in claim 3, in which the movable member is a rod engaging in an air-filled aperture having a closed end and transverse to the pin, and also engaging the bottom of a recess in the supporting member, said rod in normal locking position serving to compress the air in the transverse aperture, the pressure of said air resiliently urging the rod to engage the bottom of the recess; and said rod being urged out of the recess by fluid pressure exerted upon the end of the rod, and encountered during the descent of the firing mechanism.

References Cited in the file of this patent UNITED STATES PATENTS 2,705,920 Kanady Apr. 12, 1955 2,859,697 Long Nov. 11, 1958 2,883,932 Caldwell Apr. 28, 1959 

